Current belt fasteners utilizing staples can be formed from a blank strip of metal which is cut and bent so as to form a strip of connected fasteners with each individual fastener in the strip having a generally flat upper and lower plate joined by arcuate hinge loops. The hinge loops form slots between each other which can receive loops of fasteners attached on another belt end for joining the belt ends together.
To attach the fasteners to a belt end, the belt end is inserted between the upper and lower plates. A belt stop extends from one of the plates to limit insertion of the belt end between the plates. The fasteners upper and lower plates are provided with staple-receiving holes or apertures. When the upper and lower plates are clamped about a belt end, the apertures will be aligned with each other to allow a generally U-shaped staple to be inserted through the aligned apertures in the upper plate of the fastener, through the thickness of the belt end, then through the aligned holes in the bottom plate of the fastener. The portions of the staple legs protruding from the bottom plate are then clinched against an anvil surface to prevent withdrawal of the staple.
After fastener strips are attached to belt ends to be coupled to one another, the belt ends are brought together with the arcuate hinge loops of the fasteners on one belt end inserted into the slots formed between the arcuate hinge loops of the fasteners secured on the other belt end, and vice versa. With the respective arcuate hinge loops in the above mating relation to one another, they cooperate to define a throughbore into which a hinge pin can be inserted to maintain the fasteners in their mated position.
In order to facilitate and speed the insertion of staples into the fasteners described above and the attachment of the fasteners by way of the staples to the belt end, various arrangements of staple guide blocks with anvil surfaces have been proposed. The guide blocks have staple-receiving channels which can be aligned with the apertures in the upper plate of the fasteners such that with the staples inserted therein, the staples will be guidingly slid through the channels so that the pointed ends of the staples project through the apertures in the upper plate of the fasteners. Thereafter, a staple driving tool is driven downwardly through the channels to drive the legs of the fasteners through the belt end and into aligned holes in the underlying lower plate of the fastener supported by the anvil. Examples of such installation tools are shown in U.S. Pat. Nos. 4,111,080 and 4,333,217, both commonly assigned to the assignee herein.
The step of individually loading each of the staples into the guide block of the installation tool can be fairly time consuming and; as such, it is known to preassemble the staples to a strip of plate fasteners in an effort to save time in the attachment process. In these prior plate fasteners having preassembled staples, the staples were mounted in the upper plate apertures with an interference fit simply by increasing the size or diameter of the wire from which the staples were fabricated. The use of heavier gauge material in forming staples drives up staple costs and generally increases the force required to be applied to the staples for driving through belt material and accordingly is not desirable.
With prior plate fasteners having preassembled staples, the staples were supported in the upper plate apertures by generally planar edges around the holes. Pre-mounting of the staples to the upper plate of the fasteners in this manner caused problems as the planar edges supported each of the staple legs at a single point of interference fit along their length. A problem with this type of interference fit is that staples may become loose from the fasteners during shipping so that the staples are misaligned or missing from the fasteners requiring time to correct or replace these staples. Thus, there is a need for an improved interference fit between the staple legs and the upper fastener plate. If the staples are pushed downwardly relative to the upper plate during shipping, the lower ends of the staples may obstruct or block the opening between the upper and lower plates preventing the belt end from being inserted therebetween.
The previously-mentioned '080 and '217 patents disclose apertures in the upper plate which are sized sufficiently large so as to allow the staple legs to pass through the apertures without significant interference and bearing against the aperture edges, and into contact with the belt before being driven therethrough with the driver, as described earlier. An important consideration in design of belt fasteners is the durability and strength of the gripping force exerted by the fastener on the belt end. For example, it is generally understood that as the staples are positioned farther from the edge of the belt, the strength of the attachment is increased, e.g., because unravelling and/or pull-out problems are diminished. One manner of improving the gripping force is by coining or inclining the outboard ends of the upper and lower plates towards one another so that when the fasteners are secured to the belt, the ends of the plates grip into the surface of the belt.
Typically, the apertures for the staples in the plate fasteners are provided in recessed areas, or pockets, formed in respective upper and lower plates so as to provide the fastener with a low profile. In other words, when the staple is driven through the belt material to secure the plate-type fastener on the belt end, the staple head or bight will seat in the upper plate pocket with the protruding ends of the staple legs clinched in the lower plate pockets so that neither the head nor legs protrude from their respective pockets. In this manner, the fastener can be provided with a relatively low profile relative to the belt end as the staple portions seated in the pockets of the upper and lower plates do not project above the plane of the generally flat, relatively thin fastener plates.
In plate fasteners of the type described above, the larger holes formed in the pockets, particularly in the upper plate, to allow the staple legs to slide therethrough, tends to minimize the material in the pocket between the holes. In addition, as the holes are formed near the outboard ends of the plates, the coining of the outboard ends can cause material to be drawn from around the aperture edges further minimizing the fastener material therearound. Thus, there is a need for a better formed pocket and holes in the pocket.